1. Field of Invention
The present invention relates to a tree stump grinding apparatus. More particularly, the invention relates to a stump grinding apparatus that includes a wheel and a plurality of blocks attached to the wheel that hold a cutting tooth.
2. Description of Related Art
Conventional stump grinding machines comprise a vertically oriented rotatable wheel having a plurality of cutting teeth mounted on the sides and/or the peripheral edge thereof. The rotating wheel is moved toward a tree stump, typically using an extension arm or boom. The cutting teeth mounted on the rotating wheel contact the tree stump and grind or cut away the stump until it is completely removed.
During normal operation of the stump grinder, the cutting teeth are subjected to large impact and abrading forces, which can cause the teeth to break off or wear out. When this occurs, one or more teeth, and sometimes the entire wheel, must be replaced. Replacement of stump grinding teeth can be a time consuming process, in part because the radial projection of each tooth must be adjusted to a predetermined, optimum value before fastening the tooth to the wheel. Replacement of the entire wheel is more time consuming and costly than simply replacing worn out or broken teeth.
In some prior art stump grinding devices, cutting teeth are directly fastened to the rotary wheel using fasteners or by welds. If the tooth is fastened to the wheel using a bolt, for example, then the bolt is solely responsible for holding the tooth to the wheel. If the impact force applied to the tooth is larger than the bolt's shear strength the bolt will fail and the tooth will shear away from the wheel. In such arrangements, the wheel can also be damaged when a large impact force is applied to one or more teeth. The impact force on the tooth is communicated directly to inner surfaces of the wheel that define the hole that receives the bolt. The impact force may cause the hole through which the bolt passes to misshape or enlarge. Consequently, the fit of a replacement bolt may become loose and subject the tooth and wheel to additional damage.
Mounting the tooth to a block on the periphery of the wheel does not provide a suitably thick section on which to fasten the tooth. Because there is no thick wheel portion to support the block, and further to support the tooth, there is an increased likelihood that the tooth and block may be sheared from the wheel.
With reference to teeth that fasten directly to the wheel, a proper seat of the tooth against the wheel is desirable. Teeth that are formed from cast metal sometimes have protuberances and bumps that, although small, preclude a flat surface-to-surface contact between the tooth and the wheel. This can allow play between the tooth and the wheel and can exacerbate the effect that the impact force has on the tooth. Also, moisture can wick under the tooth to create rust and corrosion.